The present invention relates to a parts handling device with at least one holding magnet for holding a part or workpiece while being handled, said holding magnet having a coil by means of which a change of the magnetic field, due to the movement of a ferromagnetic part relative to the coil, can be sensed and utilized to initiate control functions.
A parts handling device comprising a non-magnetic belt conveyor and holding magnets disposed behind said belt conveyor and exerting a force on the parts or workpieces to be handled which presses them against the belt conveyor has been suggested heretofore. According to this prior suggestion, at least one of the holding magnets, which may be designed as permanent magnets or as D.C. or A.C. supplied electromagnets, is provided with a coil giving a signal in response to changes of the magnetic field which signal is used to control the path of the part being handled. The coil may be employed as a self-generating pick-up if the parts to be handled are magnetized, because a part passing the coil will then induce a voltage surge in the coil which can be utilized as control signals. As a rule, however, the coil is A.C. supplied and the change of the leakage or stray field of the coil, effected by the approach of a ferromagnetic (magnetized or not magnetized) part or workpiece, is utilized to form a control signal. The approach or withdrawal of a ferromagnetic part influences the inductance of the coil which can be measured, with the variation of the measured value providing the control signal, or which leads to a change of the passing current at constant supply voltage or a change of the coil voltage at constant supply current, said change of current or voltage serving as control signal. However, this principle of using a voltage surge induced in a coil or the inductance variation of a coil of a parts handling device upon approach or withdrawal of a ferromagnetic part for the generation of control signals is not limited to handling devices incorporating a belt conveyor, nor is the application of this principle restricted to controlling the path of the part to be handled.
It is an object of the present invention to expand the scope of the application of the aforementioned principle in connection with parts handling devices in order to impart certain advantageous properties to the parts handling devices so equipped.